Underreamer having unequal arm extension radii



Dec. 16, 1969 a H. FUCHS 3,483,934

UNDERREAMER HAVING UNEQUAL ARM EXTENSION RADII Filed May 1968 2 Sheets-Sheet 1 /5 A flrchZ.

BENJAMIN H Fae/4.5

ZNVENTOE.

Dec. 16, 1969 B. H. FUCHS 3,483,934

UNDERREAMER HAVING UNEQUAL ARM EXTENSION RADII Filed May 1968 2 Sheets-Sheet 2 IN a/E/v T02 BEM/nM/N H. fucws 3ml %/m/ United States Patent 3,483,934 UNDERREAMER HAVING UNEQUAL ARM EXTENSION RADII Benjamin H. Fuchs, 3842 Rose Ave.,

Long Beach, Calif. 90807 Filed May 6, 1968, Ser. No. 726,882 Int. Cl. E21b 9/26, 9/32 US. Cl. 175267 7 Claims ABSTRACT OF THE DISCLOSURE An underreamer for enlarging a well bore wherein a plurality of cutter cones are rotatably supported on pivoted arms which swing outwardly from the body of the tool different radial amounts, thereby disposing the respective cutter cones in radially stepped relationship. This permits a greater radial spread of the cutter working surfaces, and hence greater bore enlargement relative to the contracted diameter of the tool, than the conventional practice of extending all of the cutters out to the same radial extent.

BACKGROUND OF THE INVENTION Underreamers are employed extensively for enlarging portions of the well bore in oil and gas wells, for various purposes, as for example to provide clearance for running casing, to obtain adequate annular space in the hole for cementing, to enlarge zones for gravel pack completion, and for other purposes.

Conventional underreamers employ three cutter cones that are rotatably supported on respective pivoted arms which swing from an initial retracted position wherein the arms and cutter cones are completely withdrawn into the body of the tool outwardly to an extended or expanded position wherein the cutter cones project radially outwardly from the body of the tool so as to enlarge the existing bore. In such conventional underreamers the cutter cones are all of the same length in the radial direction relative to the body of the tool. Similarly, in conventional underreamers the three pivoted arms upon which the cutter cones are rotatably supported swing outwardly to the same radial extent. The length of the cutters is strictly limited in such conventional underreamers by the requirement that the cutters all fit completely within the diameter of the body of the tool when in the retracted position, and the amount of hole enlargement that can be accomplished is, in general, limited to the cutter length since the cutters must generally operate upon the full annular formation area between the wall of the original bore and the wall of the enlarged bore.

It can thus be seen that conventional underreamers having cutter cones of equal lengths and cone support arms which swing outwardly to equal extents are rather strictly limited in the amount of bore enlargement which they can achieve. Nevertheless, it is desirable with this type of tool to obtain the largest possible effective cutting diameter relative to the retracted tool diameter; i.e., it is desirable to obtain the maximum possible outward extension of the cutters consistent with efficient cutting and durability of the cutters in operation.

One prior art attempt to obtain a greater amount of cutter extension than with conventional underreamers of the type described hereinabove involved the use of two relatively short cutter cones and one relatively long cutter cone which was substantially longer than conventional cones used for underreamers of similar body size. With this arrangement, the long cutter nested between the two short cutters in the retracted position,

3,483,934 Patented Dec. 16, 1969 yet in the extended position the long cutter permitted a greater cutting area to be covered. However, with this arrangement all three of the cutters were swung outwardly to the same radial extent, with the long cutter being the only one operating upon the full annular formation area between the wall of the original hole and the wall of the enlarged hole, the two short cutters only operating upon the outermost part of such annular for mation. This resulted in the small end of the large cutter doing the entire cutting work on the inner annular portion of the formation area adjacent the original hole. This not only placed an undesirable limitation upon the cutting speed, but since the small end of a cone type of cutter is, in general, substantially weaker than the large end, it placed an undue burden upon a relatively Weak portion of the device, tending to overload the small end of the large cutter, and thereby impairing the reliability and durability of the device as compared with conventional underreamers.

SUMMARY OF THE INVENTION In view of these and other problems in the art, it is an object of the present invention to provide a novel underreamer having a plurality of cutter support arms which swing outwardly from the body of the tool differenct amounts so as to dispose the respective cutters in radially stepped relationship and thereby obtain a greater radial spread of cutter surface and provide greater bore enlargement relative to the contracted diameter of the tool than with conventional underreamers wherein the arms all swing out the same distance.

Another object of the invention is to provide an underreamer of the character described wherein the use of unequal cutter cone support arm extension radii permits conventional cutter cones of standard, equal lengths to be employed, despite the fact that the bore can be reamed out to a substantially greater extent than was heretofore possible with such conventional cutters of equal lengths.

Another object of the invention is to provide an underreamer of the character described wherein a plurality of roller cutter cones are arranged during the cutting operation at different extension radii relative to the axis of the tool, in such a way that a relatively large portion of an inner cone leads the small end portion of an outer cone in generally overlapping relationship, whereby the relatively tough larger portion of the inner cone protects the weaker small part of the outer cone by working in advance thereof.

A still further object of the invention is to provide an underreamer of the character described which embodies three cutter cones that, in operation, are disposed in three generally overlapping radial positions, whereby able.

Further objects and advantages of this invention will appear during the course of the following part of this specification, wherein the details of construction and mode of operation of a preferred embodiment are described with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a vertical, axial section, with portions in elevation, illustrating an underreamer embodying the present invention, with the cutter arms disposed in their collapsed or withdrawn positions.

FIGURE 2 is a horizontal section taken on the line 22 in FIGURE 1.

FIGURE 3 is a horizontal section taken on the line 33 in FIGURE 1.

FIGURE 4 is a vertical, longitudinal section, with portions in elevation, taken on the line 4-4 in FIGURE 3, illustrating two of the cutter arms and their respective cutter cones in their collapsed or withdrawn positions.

FIGURE 5 is a vertical, longitudinal section similar to FIGURE 4, but illustrating the underreamer of FIG- URES 1 to 4 in operation enlarging a bore, with the two cutter arms illustrated in FIGURE 4 swung outwardly different amounts in their extended, operative positions, to place the respective cutter cones at different extension radii.

FIGURE 6 is a horizontal section taken on the lin 6-6 in FIGURE 5, illustrating the overlapping cutting relationship of the three cutters disposed at different, stepped radial positions.

DETAILED DESCRIPTION Referring to the drawings, an expandable underreamer embodying the present invention is generally designated 10, and includes a tubular, elongated body 12 which is threadedly connected to a suitable tubular top sub 14.

Three cutter arms, 16, 18 and 20, are longitudinally arranged at regularly spaced intervals about the tubular body 12 in the lower portion thereof, the arms 16, 18 and 20 being supported in respective elongated slots 22, 24 and 26 in the body 12. The cutter arms 16, 18 and 20 are pivotally supported proximate their upper ends to swing generally in respective vertical planes which are radially oriented relative to the axis of the body 12, on respective horizontal support pins 28 which are mounted in the body 12. The cutter arms 16, 18 and 20 are provided with arcuate upper ends which are seated in complementary recesses in respective arm retainers .30 which are bolted or otherwise secured to the body 12.and serve as thrust bearing means for applying drill string weight to the cutters. Conventional cutter cones 32, 34 and 36, which, if desired, may be the same length, are rotatably mounted at the lower ends of the respective cutter arms 16, 18 and 20.

A wash barrel 38 is axially centered within the tubu lar body 12, being slidably supported near its lower end in a bushing 40, and having a piston 42 secured to its upper end portion, the piston 42 being slidable within an enlarged cylinder 44 in the tubular body 12. In the collapsed or retracted position of the underreamer as shown in FIGURES l and 4, the wash barrel 38 and piston 42 are in an uppermost position, while in the expanded or fully operative position of the tool as illustrated in FIGURES 5 and 6, the wash barrel 38 and piston 42 are in a lowermost position which is defined by engagement of the piston 42 against an upwardly facing shoulder 46 at the bottom of the enlarged cylinder 44. An intermedate enlargement 48 in the bore of body 12 provides seating for a helical spring 50 which biases the piston and wash barrel toward their uppermost positions as illustrated in FIGURES 1 and 4. The piston 42 and wash barrel 38 are normally in the uppermost position of FIGURES 1 and 4, but may be selectively moved downwardly to the position of FIGURE 5 by the introduction of drilling fluid under pressure through the sub 14 and into the cylinder 44.

Three cams, 52, 54 and 56, project radially outwardly from the wash barrel 38, the cams 52, 54 and 56 being integrally connected to the wash barrel 38 as by welding, and being regularly spaced about the Wash barrel so that the cams 52, 54 and 56 are in alignment with the respective cutter arms 16, 18 and 20. The arms 16, 18 and 20 have generally radially inwardly facing cam follower surfaces 58, 60 and 62 thereon, respectively, which are engaged by the respective cams 52, 54 and 56 upon downward movement of the piston 42 and wash barrel 38, and consequently of the cams, to move the cutter arms 16, 18 and 20 from their fully retracted positions as illustrated in FIGURES 1 and 4 outwardly to their expanded or extended, operative positions as illustrated in FIGURES 5 and 6. The cam follower surfaces 58, 60 and 62 terminate at their lower ends in respective cam ledges 64, 66 and 68 against which the cams abut for holding the cutter arms in their fully extended or full swing positions as illustrated in FIG- URES 5 and 6.

In the form of the invention that is illustrated in the drawings, the three cams 52, 54 and 56 are of equal radial height, and the cutter arms 16, 18 and 20 are caused to swing outwardly different amounts by relative differences between the three respective cam follower surfaces 58, 60 and 62. Thus, the cam follower surface 58 is the steepest of the three, and its respective ledge 64 is positioned radially inwardly on the arm 16 further than the others, whereby the cutter arm 16 and its respective cutter cone 32 are cammed outwardly to the greatest extension radius of the three.

Conversely, the cam follower surface 60 has the least incline of the three cam follower surfaces, and the respective ledge 66 is disposed radially outwardly in the arm 18 further than the other two ledges, whereby the arm 18 and respective cutter 34 are cammed outwardly to the smallest extension radius of the three.

The cam follower surface 62 has a slope which is intermediate the slopes of surfaces 58 and 62, and the ledge 68 is disposed at a radial position in its respective arm 20 which is intermediate the positions of the ledges 64 and 66. Accordingly, the cutter arm 20 and its respective cone 36 are cammed outwardly to an extension radius that is intermediate the radii of arm 16 and its cutter 32 on the one hand, and arm 18 and its cutter 34 on the other hand.

While the cutter arms are thus swung outwardly different amounts by cam members which are the same size operating against cam surfaces and ledges that are in different relative positions on the respective arms, alternatively the cam follower surfaces and ledges on all three arms may be the same, and the different radial extension of the three arms may be accomplished by employing three cams corresponding to the cams 52, 54 and 56 which are of different heights.

Cooperating with the aforesaid cam means for positively moving the cutter arms and respective cones outwardly to different operating radii are opposed shoulders engageable between the body 12 and the respective cutter arms 16, 18 and 20 to positively limit the amount of radial extension of the arms. This shoulder means includes pairs of generally radially inwardly directed, inclined stop shoulders 70, 72 and 74 in the body 12 which are engageable with respective pairs of generally radially outwardly facing, inclined shoulders 76, 78 and on the respective cutter arms 16, 18 and 20. In the form of the invention illustrated in the drawings, the body stop shoulders 70, 72 and 74 are all similarly positioned and oriented, while the cutter arm shoulders 76, 78 and 80 are arranged at different angles and radial positions on each of the three cutter arms 16, 18 and 20, so as to cooperate with the previously described cam means to positively locate the three cutter arms, and hence the respective cutter cones, in their three different radial positions during operation. Thus, the shoulders 76 on cutter arm 16 are the innermost of the three pairs of arm shoulders, with the mildest angle of inclination, whereby the arm 16 may be cammed outwardly the greatest amount of the three arms. Conversely, the shoulders 78 on the arm 18 are the outermost of the three pairs of arm shoulders, with the steepest incline, thereby allowing the least amount of radial outward movement of the arm 18. The shoulders 80 on the arm 20 are intermediate the shoulders 76 and 78, thereby allowing an intermediate amount of swinging movement of the arm 20.

It will be apparent that if desired, the shoulders on the cutter arms may all be positioned alike, and the stop shoulders in the body may be varied in radial position and orientation to stop the three cutter arms in their respective differing radial operative positions.

Three fluid passages 82 extend longitudinally through the body 12 from respective entrances 84 located in the upper end of the enlarged cylinder 44 to respective jet orifices or outlets 86 that are located as close as is practical above the cutter cones. Each of the jet orifices 86 opens into a recess in the outer surface of body that is formed by a downwardly and outwardly curving guide surface 88. These jet guide surfaces 88 provide a convenient means for directing the jet flow of pressurized fluid in a downwardly and outwardly diverging stream, and these jet guide surfaces may be considered as forming a part of their respective jet orifices.

Preferably, the fluid passages 82 are circumferentially disposed in the body 12 intermediate the cutter arms 16, 18 and 20, as best illustrated in FIGURES 2 and 3. Similarly, the jet orifices 86 are circumferentially arranged about the body 12 intermediate the cutter arms 16, 18 and 20, and immediately above the cutter cones 32, 34 and 36. Thus, when the tool is rotating during a cutting operation to ream a portion of a hole out to an enlarged portion as illustrated in FIGURE 5, each of the cutting cones is led by a jet stream which is directed generally into the region of the cutting plane, and in this manner the jet stream will provide a full highvelocity washing flow directly in the region of the cutting ledge where it is most effective, the flow being unimpaired by any structure on the underreamer or by the ledge itself. Since each of the three cutter cones 32, 34 and 36 is operating at a different average radial position on the ledge, it is desirable for each of the jet orifices 86 to be arranged to direct its jet stream at a radius which is most effective for the average radius of the cone which follows it as the tool rotates.

In the inoperative or retracted position of the underreamer as it is being lowered through the hole to a desired region of operation, drilling fluid will not be pumped through the sub 14 into the cylinder 44, and hence the biasing force of spring 50 will hold the piston 42, wash barrel 38 and cams in their uppermost positions as illustrated in FIGURES 1 and 4, these positions being defined by engagement of the cams 52, 54 and 56 against shoulders 90 in the cutter arms. In this inoperative or retracted condition of the underreamer the three cutter arms are held in their collapsed or retracted positions as shown in FIGURES 1 and 4 by gravity, and also by the spring biased engagement of the cams 52, 54 and 56 against the shoulders 90 in the respective cutter arms 16, 18 and 20.

When the tool is at the desired position in the hole to commence reaming, the tool is rotated and drilling fluid is introduced under pressure through the sub 14 into the cylinder 44. Some of this drilling fluid will pass on downwardly through the Wash barrel 38 and thence through the hollow lower portion of the body 12 into the hole below the underreamer, and the flow of this fluid back upwardly around the tool will wash away the cuttings which are relatively free and which are freed by the jet streams provided from the orifices 86. Preferably, there is a constriction 92 in the wash pipe which serves to build up fluid pressure in the cylinder 44 so as to more effectively actuate the cutters and provide high pressure and velocity to the jet streams from orifices 86.

The fluid pressure in cylinder 44 will force piston 42 downwardly from the position of FIGURES 1 and 4 to the position of FIGURE 5, which will in turn move wash barrel 38 and cams 52, 54 and 56 downwardly so as to swing the respective cutter arms 16, 18 and 20 outward- 1y to their operative positions. The pressurized fluid in cylinder 44 will also cause fluid to be forced through the fluid passages 82 from entrances 84, and thence out through the jet orifices 86 which direct the jet streams divergently downwardly and radially outwardly in the general region of the cutting plane.

It will be noted from FIGURE 5 that the small, relatively Weak inner end portion 94 of cutter 32 operates In a similar manner, by having all three of the cutters, 32, 34 and 36 located in different, but generally overlapping radial positions, the extra work of cutting a considerably larger diameter than that which is cut by conventional underreamers is generally evenly distributed to the three cutters. In test boring I have found that it is preferable to somewhat concentrate the cutter strength toward the outer part of the ledge. This can be accomplished by having the radial position of the intermediate cutter cone 36 somewhat closer to that of the outer cone 32 than to the inner cone 34. In one test tool which proved to be highly efficient and durable, the operating diameters for the outer edges of each of the three cones 32, 34 and 36 were, respectively, 15 inches, 14 inches andl2% inches. If desired, the outer two cones may be disposed at the same diameter, and the tool will still enable a considerably larger underreaming diameter to be achieved than can be achieved with conventional equipment.

While the instant invention has been shown and described herein in what is conceived to be the most prac tical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims, so as to embrace any and all equivalent devices.

I claim:

1. An expandable underreamer which comprises an elongated, generally cylindrical body adapted to be suspended from and rotatably driven by a drill string, first and second roller cutter cones mounted on said body in peripherally spaced relationship with each cutter cone having a large outer portion and a small inner portion, both of said cutter cones being selectively movable between an inoperative position generally retracted into said body and an operative position projecting generally radially outwardly from the body, said cutter cones being supported on respective first and second arms, said arms being arranged generally longitudinally of said body and being pivotally connected to the body adjacent their upper ends and supporting the respective cutter cones thereon adjacent their lower ends, said arms being pivotal between an inoperative position corresponding to said inoperative position of the cutter cones wherein said arms are generally recessed within elongated slots in the body and an operative position corresponding to said operative position of the cutter cones wherein the arms incline downwardly and radially outwardly from their pivotal connections with the body, the pivot axes of said arms being substantially horizontally coplanar and said arms having substantially the same length, said first arm swinging outwardly to a substantially greater angle relative to the axis of the body than said second arm in said operative position of the arms so as to dispose said first cutter cone outwardly from the axis of the body to a substantially greater extent than said second cone defining an annular cutting area during rotation of the body that radially overlaps and axially leads the annular cutting area of said small inner portion of said first cutter cone.

2. An expandable underreamer as defined in claim 1, which includes a third arm arranged generally longitudinally of the body in peripherally spaced relationship to said first and second arms, said third arm having substantially the same length as said first and second arms and being pivoted to the body adjacent its upper end on a pivot axis substantially horizontally coplanar with the other said pivot axes, and a third roller cutter cone supported on said third arm adjacent the lower end thereof, said third arm being pivotal between an inoperative position wherein it is generally recessed within an elonggated slot in the body and said third cone is generally retracted into said body and an operative position wherein it inclines downwardly and radially outwardly from its pivotal connection with the body and said third cone projects generally radially outwardly from the body.

3. An expandable underreamer as defined in claim 2, wherein all three of said cutter cones in said operative positions of the arms are located in different but generally overlapping positions relative to the axis of the body.

4. An expandable underreamer as defined in claim 2, wherein said third cutter cone in said operative positions of the arms is disposed outwardly from the axis 8 of the body to a greater extent than said first cutter cone, but wherein the spacing between said first and second cones is greater than the spacing between said first and third cones relative to the axis of the body.

5. An expandable underreamer as defined in claim 2, wherein said third cutter cone in said operative positions of the arms is disposed outwardly from the axis of the body to substantially the same extent as said first cutter cone.

6. An expandable underreamer as defined in claim 1, which includes cam means in the body engageable with cam follower surface means on said arms to swing said arms outwardly from the body.

7. An expandable underreamer as defined in claim 6, which includes shoulder means in the body engageable with opposed shoulder means on said arms to positively limit the extent of outward movement of the arms.

References Cited UNITED STATES PATENTS 2,499,916 3/1950 Harris 175267 2,654,575 10/1953 Kammerer 175266 3,171,503 3/1965 Shirley 175-269 3,356,167 12/1967 Trent 175267 X FOREIGN PATENTS 838,833 6/ 1960 Great Britain.

NILE C. BYERS, JR., Primary Examiner 

